Fix crash when login results in error.
Merge pull request #15 from learning-layers/hotfix/login-error-crash

This fixes the original problem, but this is still not handled neatly. Merging this for now. I will open a new issue for improving usability of logins once the video browsers nativity improvements are done.
Clean up InformationFragment.
Clean up resources.
Add new media playback icons.
Modularise video and annotation rendering.

- Playback happens in VideoPlayerFragment.
- Playback is controlled by VideoPlayerActivity.
- Annotations are handled by AnnotationRenderService.
- MarkerRenderer places native views onto a MarkerCanvas.
Implement pinch to zoom for videos.

Video is now drawn on a TextureView.
Replace FloatPosition with Android's PointF.
Move pinch to zoom into a custom ViewGroup.

Now uses GestureDetectors to detect zooming and panning.
Tweak subtitle style.
Remove `google-api-client-android` dependency.

No longer needed since `NetHttpTransport` is readily available on all
supported versions of Android.
Update OkHttp to 2.1.0.
Track upload progress using just Okio.

Also flushes the double-buffered sink properly.
Merge pull request #18 from learning-layers/improvement/okhttp-okio

Networking-related improvements
Fix marker canvas touch events.
Focus of scaling is now in the right place (in the center of the pinch
gesture)
Fix annotation position bound checking.
Clean up VideoPlayerFragment.
Add missing override annotation to MarkerCanvas.
Use new icons for playback controls.